Water-Source Heat Pumps Go to School
Several years ago, the student body of School District 159 was expanding to the point that a new middle school became an obvious necessity. The district commissioned KJWW Engineering Co. of Naperville, Ill., to perform an initial feasibility study and come up with a schematic design and recommendations for essential items, including the heating and cooling system.
"I was involved with KJWW at a very early stage of the project," said Jay Samuelsson of Imbert Corp., ClimateMaster's commercial representative in the Chicago area. "And I've also interacted very closely with Globetrotters Engineering from the point that Globetrotters became the engineering firm of record, seeing the project through to completion.
"Among the things people can often overlook is the importance of funding. Because our ClimateMaster systems require a higher initial investment, we need to be aware of various funding options that are available. Yes, our ClimateMaster products represent substantial anticipated operating-cost savings over the life of the system. But there can also be a lot of initial-cost resistance up front."
In the case of Colin L. Powell Middle School, ClimateMaster's higher initial cost was largely offset by a grant - awarded for energy-saving technology - from an Illinois clean energy organization.
"To get the grant and secure the funding takes time and persistence, as well as knowing it's available," said Samuelsson. "In the past, many people probably wouldn't go to that level. But now there's more pressure coming from state and local governments to begin to look more seriously at this kind of technology."
The project involved a total capacity of 280 tons (985 kW) of water-to-air and 180 tons (633 kW) of water-to-water heat pumps - with outside-air energy-recovery air handlers adding to the efficiency of the overall design.
"One of the biggest points in favor of using this type of system is the fact that we were using a renewable energy source for both heating and cooling," said Jerry Gillette, P.E., project manager of Globetrotters Engineering Corp., Chicago.
For overall control of the building's heating and cooling, the school district selected ClimateMaster's direct digital control with DXM boards and tied it into a larger building automation system that controlled lighting and all other electrical functions.
"Often with heat pump systems in the Midwest, you have to provide for supplemental heat in the extreme wintertime," he noted. "We don't think we'll need that because we're getting the heat source from the pond. And with the compressor inside the heat pump, we can do things that will extract enough heat so we don't have to purchase additional heating capacity from the electrical utility, Commonwealth Edison."
Built into this project is a 780 kW boiler for emergency-heating purposes in case the temperature gets all the way down to -40Â°F (-40Â°C). The boiler may have to be used when it gets down as low as -20Â° (-29Â°).
"But as part of our research, we visited a high school in Wisconsin - where it definitely gets colder than it does in the Chicago area - and on that system they have two boilers that they rarely have to fire up. I don't think we often will here, either."
Conservative estimates place the payoff period during which the school district's operating-cost savings with the ClimateMaster water-source heat pump system will totally offset the initial-cost premium at no longer than seven years.
"It's really a win-win all around," commented Gillette. "The school district is going to benefit. The students and their parents are going to benefit from a more favorable climate in the academic environment, and a seven year payoff is actually very good for an investment in major cutting-edge equipment such as this."
After the design and construction of Colin L. Powell Middle School, the district was confident that the facility would serve as a prime example of 21st-century energy-efficiency foresight in action.
"The school district chose water-source heat pumps because - in addition to the district's desire for the latest energy-efficient system - there was already a storm water-retention pond on the site the district had purchased," said Gillette. "So we expanded the pond to meet the required water-source flow characteristics."
The pond, which is the source of the geothermal system's water-to-water heat exchange capability, also lends a certain aesthetic appeal to the site.
"I hired a consultant to perform the fluid-mechanic studies and calculations for the required pond characteristics," noted Gillette. "Those calculations were based on water capacity and anticipated ambient temperatures at certain depths year-round.
"Obviously, you have to take both wintertime and summertime conditions into consideration. And we installed a groundwater-well pump in case the level of the pond might fall so low during a potential drought that we'd need to pump more water in to fill the pond, which has to be maintained at a depth of approximately 14 feet to accommodate the system's required flow."
The overall size of the completed school building is 160,000 square feet and it contains 82 ClimateMaster installed water-source heat pump units. Expected annual operating-cost savings using the water-source heat pump system are estimated at around $70,000.
Future plans are to submit the school building and its architectural design for Leadership in Energy and Environmental Design (LEED) certification as administered by the U.S. Green Building Council in Washington. Gillette also has plans to directly impact student learning opportunities.
"As part of our control of the heating and cooling system, we set up a weather-monitoring system at the school to monitor weather patterns that affect the pond," he said. "So I've contacted several of the broadcast outlets in Chicago to see if any of them will commit to have Powell Middle School as one of their sites for monitoring and reporting on weather conditions.
"This could be a fantastic chance to introduce young students to the basics of meteorology - and perhaps lead to career possibilities in future years. And it's all because we have this state-of-the-art energy-saving ClimateMaster water-source heat-pump system in place."
Publication date: 10/09/2006